I know it is probably staring me in the face, but where is the thermostat located in the 1999 Impreza.

In the lower radiator hose housing that bolts onto the engine.

Follow the lower radiator hose from the radiator and you'll see the housing. It's held on by two bolts. Take them off, and pull the housing down, and you'll find your t-stat.

josh

Just drop all the fluid from the radiator first before removing the housing.

Unless you like being covered in the coolant with no easy way of stemming the flow.